Illumination device, projection type image display device, and optical device

ABSTRACT

To provide an illumination device and a projection type image display device that illuminate an area to be illuminated (image formation area) under conditions where speckle noise is less noticeable. 
     An illumination device according to the present invention includes: a light source  11  that emits coherent light; an optical scanning section  15  that scans the coherent light emitted from the light source  11 ; a lens array  22  including a plurality of element lenses and configured to diverge the light scanned by the optical scanning section; an optical path conversion system  23  configured to control a diverging angle of the diverging light to be emitted from respective points of the lens array  22  and to allow the diverging light whose diverging angle has been controlled to illuminate an area to be illuminated sequentially in an overlapping manner.

TECHNICAL FIELD

The present invention relates to an illumination device that usescoherent light such as laser light, a projection type image displaydevice that uses the coherent light to illuminate an optical modulationelement to project an image on a screen, and an optical device for usein the illumination device and projection type image display device.

BACKGROUND ART

There is known a projector (projection type image display device) thatuses an optical modulation element (micro display) such as a liquidcrystal or MEMS to visualize illumination light from a light source andprojects an image based on the illumination light on a screen. Some ofsuch projectors use, as its light source, a white light source such as ahigh-pressure mercury lamp and projects an image on a screen whilemagnifying an image obtained by illuminating a two-dimensional opticalmodulation element such as a liquid crystal.

However, a high-intensity discharge lamp such as the high-pressuremercury lamp has a comparatively short life, so that when thehigh-intensity discharge lamp is used for a projector, the lamp needs tobe replaced frequently with new one. Moreover, the use of thehigh-intensity discharge lamp disadvantageously increases a size of theprojector. Moreover, it is unfavorable to use the high-pressure mercurylamp that uses mercury, in terms of environmental burden. To solve suchdrawbacks, a projector that uses laser light as its light source isproposed. A semiconductor laser has a longer life than the high-pressuremercury lamp and allows size reduction of the entire projector.

The laser light thus expected to be used as a next-generation lightsource for projector is excellent in linearity, so that it is consideredthat incidence rate can be enhanced more than an LED. However, in a casewhere the laser light is used as the light source, speckle noise maygenerate due to high coherence, disadvantageously making an imagedifficult to see.

The speckle noise is granular noise generated due to interference ofscattering light from a minute irregularity of a surface to beirradiated when coherent laser light is used as a light source. Thespeckle noise generated in the projector not only causes degradation ofimage quality but also provides physiologic discomfort to a viewer. Toreduce the speckle noise, various attempts, such as to vibrate adiffuser plate through which the laser light passes, to widen awavelength spectrum of laser, and vibrate a screen itself which is anirradiation target of the laser light are made. As one of such attemptsfor speckle noise reduction, Patent Document 1 discloses a non-speckledisplay device that reduces the speckle noise by rotating a diffuserplate through which coherent light passes.

PRIOR ART DOCUMENT Patent Document

Patent Document 1: JP 06-208089A

SUMMARY OF THE INVENTION Problem(s) to be Solved

The speckle noise reduction method disclosed in Patent Document 1 canaverage speckle noise (interference pattern) generated before arrival ata diffusion element. However, since an angle of incident light from adiffusion center to the screen is invariant at any point on the screen,so that light scattering characteristics at respective points on thescreen are constant, with the result that removal effect of the specklenoise generated on the screen can hardly be obtained.

Such speckle caused by the coherent light has become a problem not onlyin a projection type image display device (projector) that uses thecoherent light as a light source, but also in various illuminationdevices that use the coherent light.

An object of the present invention is to provide an illumination devicecapable of suppressing speckle generated due to use of the coherentlight as a light source and a projection type image display device usingthe illumination device. Another object of the present invention is toprovide the illumination device and projection type image display devicecapable of effectively illuminating an area to be illuminated to enhancelight utilization efficiency. A still another object of the presentinvention is to illuminate the entire area to be illuminated uniformlyby illuminating the area to be illuminated under nearly the sameconditions.

Means for Solving the Problem(s)

An illumination device according to the present invention includes: alight source that emits coherent light; an optical scanning section thatscans the coherent light emitted from the light source; a lens arrayincluding a plurality of element lenses and configured to diverge thelight scanned by the optical scanning section; an optical pathconversion system configured to control a diverging angle of thediverging light to be emitted from respective points of the lens arrayand to allow the diverging light whose diverging angle has beencontrolled to illuminate an area to be illuminated sequentially in anoverlapping manner.

In the illumination device according to the present invention, theoptical path conversion system illuminates the entire area to beilluminated regardless of a position at which the optical scanningsection scans the coherent light.

In the illumination device according to the present invention, theoptical path conversion system includes an optical element having alight collection function.

In the illumination device according to the present invention, theelement lenses constituting the lens array are each a gradient indexlens.

In the illumination device according to the present invention, theelement lenses constituting the lens array are arranged in multiple rowsin an optical axis direction thereof.

In the illumination device according to the present invention, a beamwidth of the coherent light that enters the lens array is smaller thanan interval between adjacent element lenses.

In the illumination device according to the present invention, apolarization control element is provided at an incident side or anemitting side of the lens array so as to prevent interference betweenbeams passing through the adjacent element lenses.

In the illumination device according to the present invention, anoptical element that provides a difference in optical path length so asto prevent interference between beams passing through the adjacentelement lenses is provided at the incident side or emitting side of thelens array.

In the illumination device according to the present invention, theoptical scanning section includes a galvano mirror.

In the illumination device according to the present invention, theoptical scanning section includes a polygon mirror.

In the illumination device according to the present invention, theoptical scanning section includes a variable diffraction element.

In the illumination device according to the present invention, theoptical scanning section includes a phase modulation element.

In the illumination device according to the present invention, a beamforming means is disposed between the light source and the opticalscanning section.

A projection type image display device according to the presentinvention includes: a light source that emits coherent light; an opticalscanning section that scans the coherent light emitted from the lightsource; a lens array including a plurality of element lenses andconfigured to diverge the light scanned by the optical scanning section;an optical modulation element having an image formation area in which animage is formed; an optical path conversion system configured to controla diverging angle of the diverging light to be emitted from respectivepoints of the lens array and to allow the diverging light whosediverging angle has been controlled to illuminate an area to beilluminated sequentially in an overlapping manner; and a projectionoptical system that projects the image of the optical modulation elementon a screen.

In the projection type image display device according to the presentinvention, the optical path conversion system is an imaging opticaldevice that keeps focal planes of the element lenses of the lens arrayand a pupil surface of the projection optical system in a substantiallyconjugate relationship.

An optical device according to the present invention includes: anoptical scanning section that scans coherent light; a lens arrayincluding a plurality of element lenses and configured to diverge thelight scanned by the optical scanning section; and an optical pathconversion system configured to control a diverging angle of thediverging light to be emitted from respective points of the lens arrayand to allow the diverging light whose diverging angle has beencontrolled to illuminate an area to be illuminated sequentially in anoverlapping manner.

Advantages of the Invention

According to the illumination device of the present invention, theoptical scanning section scans the coherent light to cause theillumination light to be emitted from the lens array to illuminate thearea to be illuminated at an angle changing with time. This allows thespeckle generated in the area to be illuminated to be made invisible toa viewer. Moreover, in the projection type image display deviceaccording to the present invention, the screen is also subjected toirradiation at an angle changing with time, thereby effectivelysuppressing the speckle to be generated on the screen.

Moreover, in the illumination device (projection type image displaydevice) according to the present invention, it is possible to illuminatethe area to be illuminated (image formation area) with the diverginglight which is emitted from the lens array and whose diverging angle hasbeen controlled. This allows respective sections of the area to beilluminated (image formation area) to be illuminated under substantiallythe same conditions, which, for example, allows the entire area to beilluminated (image formation area) to be illuminated uniformly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating a configuration of a projection type imagedisplay device provided with an illumination device according to anembodiment of the present invention.

FIG. 2 is a view illustrating a configuration of the illumination deviceaccording to the embodiment of the present invention.

FIG. 3 is a view illustrating a relationship between a lens arrayaccording to the present embodiment and coherent light entering the lensarray.

FIGS. 4A and 4B are views each illustrating a configuration forpreventing interference between element lenses according to anotherembodiment of the present invention.

FIG. 5 is a view illustrating a configuration of the lens array usinggradient index lenses according to another embodiment of the presentinvention.

FIG. 6 is a view illustrating a configuration of an optical scanningsection (variable diffraction element) according to another embodimentof the present invention.

FIGS. 7A and 7B are views illustrating a configuration of the opticalscanning section (phase modulation element) and a phase change in theoptical scanning section, respectively, according to another embodimentof the present invention.

FIGS. 8A to 8E are views each illustrating the phase change in theoptical scanning section (phase modulation element) according to anotherembodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

Now, an illumination device and a projection type image display deviceaccording to an embodiment of the present invention will be describedwith reference to the drawings. FIG. 1 is a view illustrating aconfiguration of a projection type image display device provided with anillumination device according to an embodiment of the present invention.It should be noted that drawings described hereinafter are each aschematic diagram, and may represent different shape, dimension, andposition from those actually illustrated.

A projection type image display device 10 according to the presentembodiment includes an illumination device 20, an optical modulationelement 31 for forming an image, and a projection optical system 32 thatprojects an image formed by the optical modulation element 31 on ascreen 41. In the drawings, a surface of the screen 41 on which an imageis projected is assumed to be X-Y plane, and an axis normal to the X-Yplane is assumed to be a Z-axis. As the screen 41, a reflective screenfor observing an image reflected by the screen 41 or a transmissivescreen for observing an image transmitted through the screen 41 can beused.

The illumination device 20 of the present embodiment includes a lightsource 11, an optical scanning section 15, a first optical pathconversion system 21, a lens array 22, a second optical path conversionsystem 23. The optical device of the present embodiment is constitutedby the constituent elements of the illumination device other than thelight source 11. It should be noted that the first optical pathconversion system 21 is not essential.

As the light source 11, various types of laser systems, including asemiconductor laser system, that emit laser light as coherent light canbe used. The coherent light emitted from the light source 11 illuminatesthe optical scanning section 15. It is preferable to provide a beamforming means for uniforming an intensity distribution of the coherentlight emitted from the light source 11 in a cross-sectional directionthereof. For example, the beam forming means is provided so as toachieve the uniformization on a surface in the vicinity of the opticalscanning section, and the optical path conversion system 21 is set suchthat the surface and optical modulation element surface are in aconjugate relationship, thereby allowing illumination of the area to beilluminated with a uniform intensity.

The optical scanning section 15 is an optical element that changes withtime a direction of the coherent light emitted from the light source 11.In the present embodiment, a galvano mirror that can rotate a reflectingsurface about a rotation center Ra is used. As such a movable mirrordevice that mechanically rotates a movable mirror, a polygon mirror, oran MEMS scanner can also be used. In addition, there can be used avariable diffraction element that electrically changes a diffractioncondition to change a light emitting direction or a phase modulationelement. Unlike the movable mirror device, such elements do not includea movable portion, so that it is possible to reduce process burden atmanufacturing time or maintenance time.

Details of this will be described later.

The optical scanning section 15 of the present embodiment has a rotationcenter Ra in a Y-axis direction and performs one-dimensional scanningthat scans the coherent light in an X-Z plane. However, the opticalscanning section 15 may perform one-dimensional scanning ortwo-dimensional scanning for the coherent light. In each case, it isnecessary for the optical scanning section 15 to scan an incidentsurface of the optical path conversion system 21 so as to consequentlysufficiently illuminate the area to be illuminated.

The coherent light emitted from the light source 11 enters the opticalscanning section 15. In the optical scanning section 15, the coherentlight becomes scanning light La whose direction is changed with time andthen enters the lens array 22 through the first optical path conversionsystem 21. In the drawing, scanning light La (t1) and scanning light La(t2) around the outermost ends are illustrated. Actually, however, thescanning light La moves between the La (t1) and La (t2) in a continuousmanner.

The first optical path conversion system 21 is an optical element thatconverts the scanning light La from the optical scanning section 15 intoscanning light La′ that enters substantially vertically an incidentsurface of the lens array 22 and is constructed using a convex lenshaving a light collection function. Making the converted scanning lightLa′ enter vertically respective element lenses constituting the lensarray 22 allows the scanning light La′ to enter the element lenses underthe same conditions. This allows the same design to be applied to allthe element lenses of the lens array 22 to reduce design burden. Thefirst optical path conversion system 21 need not always be provided. Ina case where the first optical path conversion system 21 is notprovided, configurations of the element lens constituting the lens array22 and an optical system provided on a downward side thereof are changeddepending on a state of incident light.

The lens array 22 is an optical element having a configuration in whicha plurality of element lenses are arranged at a position (on an X-Yplane) scanned by the scanning light La′ from the optical scanningsection 15. The lens array 22 is configured to convert the scanninglight La′ entering the element lenses into diverging light Lb. A sizeand a shape of each element lens constituting the lens array 22 can bechanged according to need. For example, a cylindrical lens arrayconstituted by element lenses each having a cylindrical shape or a microlens array constituted by element lenses each having an extremely smallsize may be used. Moreover, in the present embodiment, the elementlenses are arranged in multiple rows (two rows) in an optical axisdirection (Z-axis direction) thereof. The coherent light emitted fromthe light source 11 is not always parallel light, but may include ascattering component slightly deviate from a parallel state. In thepresent embodiment, to suppress the scattering component, the elementlenses are arranged in multiple rows in the optical axis direction. Theelement lenses arranged in the optical axis direction have the samediameter and have central axes parallel to a light travel direction. Thelens array 22 may have a configuration in which the element lenses arearranged in one row in the optical axis direction.

The second optical path conversion system 23 (“optical path conversionsystem” in the present invention) is an optical element that illuminatesan image formation area as an area to be illuminated with the diverginglight Lb. The diverging light Lb emitted from respective points of thelens array 22 scanned by the optical scanning section 15 passes throughthe second optical path conversion system 23 and then illuminates thearea to be illuminated sequentially in an overlapping manner.Preferably, the second optical path conversion system 23 has a lightcollection function that allows the diverging light Lb emitted from thelens array 22 to illuminate the image formation area of the opticalmodulation element 31 as the area to be illuminated. By controlling adiverging angle of the diverging light Lb diverged by the lens array 22to converge it on the image formation area, it is possible to enhancelight utilization efficiency. Moreover, preferably, the second opticalpath conversion system 23 converts the diverging light Lb into parallelor substantially parallel light. Illuminating the image formation areawith the parallel or substantially parallel light allows respectivesections of the image formation area to be illuminated undersubstantially the same conditions, which, for example, allows the entireimage formation area to be illuminated uniformly.

The second optical path conversion system 23 is only required to havethe diverging angle control function and is constructed using acombination of a mirror and a prism. Alternatively, a hologram elementor a diffraction element having an equivalent function may be used.Further alternatively, a combination of the above elements may be used.

Diverging light Lb′ emitted from the second optical path conversionsystem 23 only needs to illuminate at least a part of the imageformation area at each time point and illuminate the entire imageformation area along with the scanning performed by the optical scanningsection 15. Preferably, however, the diverging light Lb′ illuminates theentire image formation area at each time point. This allows a brightnessdistribution to be made uniform in the image formation area.

The optical modulation element 31 is a display having the imageformation area in which an image is formed based on an image signal. Inthe present embodiment, a transmissive liquid crystal element is used asthe optical modulation element 31. In addition to such a transmissivetype, a reflective type such as an MEMS can be used. The diverging lightLb′ from the second optical path conversion system 23 enters the opticalmodulation element 31 while changing its incident angle with time and isthen converted into modulated light Lc based on an image displayed inthe image formation area.

The projection optical system 32 performs magnification conversion forthe modulated light Lc to convert it into image reproduction light Ldfor projection on the screen 41. In the present embodiment, a diaphragm33 is provided at a downstream side of the projection optical system 32.Preferably, the diaphragm 33 (pupil surface of the projection opticalsystem) and focal planes of the element lenses of the lens array arekept in substantially a conjugate relationship. With this configuration,imaging optical characteristics of the beams from all the element lensescan be made uniform within a plane of the optical modulation element.

Now, an operation principle, etc., of the illumination device 20functioning as a main factor for suppressing the speckle in theprojection type image display device 10 will be described in detail.FIG. 2 is a view illustrating a configuration of the illumination device20 according to the embodiment of the present invention, which shows astate of illumination by the lens array 22.

As illustrated in FIG. 2, the scanning light La (t1) at time t1 entersthe optical path conversion system 21 and is then converted intoillumination light La′ (t1) that enters vertically the incident surfaceof the lens array 22 to be emitted therefrom as the diverging light Lb(t1). The diverging light Lb (t1) emitted from the lens array 22 isconverted by the second optical path conversion system 23 so as toilluminate at least a part of the image formation area of the opticalmodulation element 31 to illuminate that area. Similarly, the scanninglight La (t2) at time t2 is converted by the second optical pathconversion system 23 into the diverging light Lb′ (t2) to illuminate atleast a part of the image formation area. As illustrated, theillumination device 20 illuminates the area to be illuminated whilechanging with time the incident angle with respect to the area to beilluminated.

Returning to FIG. 1, the modulated light Lc modulated by the opticalmodulation element 31 is magnified by the projection optical system 32and projected on the screen 41 as the image reproduction light Ld,allowing a viewer to observe an image reflected from or transmittedthrough the screen 41. At this time, the coherent lights projected on asurface of the screen 41 interfere with each other to cause speckle.However, in the present embodiment, the coherent light is scanned by theoptical scanning section 15, which consequently sequentially changes anincident angle of the image reproduction light Ld to be projected on thescreen 41. This extremely effectively makes the speckle less noticeable.

For example, the image reproduction light Ld (t1) at the time t1 andimage reproduction light Ld (t2) enter a point P1 on the screenillustrated in FIG. 1 at different incident angles. The same can be saidfor a point P2 illustrated in FIG. 1 and other not illustrated points.That is, the image reproduction light Ld projects an image on the screen41 while changing with time the incident angle. Therefore, in anextremely short time, the speckle formed on the screen is averaged interms of time within a visual response time by the image reproductionlight Ld which is irradiated at an incident angle changing with time andthereby becomes sufficiently less noticeable to the viewer viewing theimage projected on the screen 41.

The speckle observed by the viewer includes not only the speckle thusgenerated due to scattering of the coherent light on the screen 41, butalso speckle generated on various optical elements of the projectiontype image display device 10. Such speckle is observed by the viewerwhen being projected on the screen 41 through the optical modulationelement 31. In the present embodiment, the scanning light La scans thelens array 22 to allow illumination of the image formation area of theoptical modulation element 31 as the area to be illuminated. That is,illuminating the area to be illuminated so as to isolate in terms oftime the diverging lights from respective points of the lens array 22from each other allows cancellation of phase information retained untilthe light passes through the lens array 22 and allows prevention ofinterference between the diverging lights from respective points of thelens array 22, which can make the speckle generated on the respectiveoptical elements of the projection type image display device 10sufficiently less noticeable.

As described above, in the present embodiment, the lens array 22 isscanned by the optical scanning section 15 with the scanning light La′with the scanning position changed with time. The lens array 22 isconstituted by the plurality of adjacently disposed element lenses, sothat the beams may be incident over the adjacent element lens. At thistime, outgoing lights from the element lens interfere with each other todisadvantageously generate unevenness or a stripe pattern in the area tobe illuminated.

Preferably, the following configuration is employed in order to suppresssuch interference between the outgoing lights from the element lenses.FIG. 3 is a view illustrating a relationship between the lens array 22according to the present embodiment and scanning light La′ entering thelens array 22. FIG. 3 illustrates a state where the beams of thescanning light La′ are incident over two element lenses 231 a and 231 bconstituting the lens array. As illustrated, the scanning light La′ isconverted into diverging light Lb_(—)1 and diverging light Lb_(—)2 byelement lenses 231 a and 231 b, respectively, to illuminate the opticalmodulation element 31. At this time, by setting a beam width d1 of thescanning light La′ smaller than an interval d2 between the adjacentelement lenses, it is possible to prevent the diverging light Lb_(—)1and diverging light Lb_(—)2 from being superimposed on each other tothereby suppress the interference therebetween.

In addition to the method of specifying the relationship between thebeam width d1 and element lens interval d2, the following configurationcan be employed as a means for preventing the interference between theoutgoing lights from the element lenses 231. FIGS. 4A and 4B are viewseach illustrating a configuration for preventing the interferencebetween the element lenses according to another embodiment of thepresent invention.

FIG. 4A is an embodiment in which transparent bodies 232 are provided atan upstream side of the element lenses 231 constituting the lens array22 so as to correspond to every other element lenses 231. Thetransparent bodies 232 are optical elements for differentiating anoptical path length. With this configuration, the optical path length isdifferentiated between the adjacent element lenses 231, e.g., elementlenses 231 a and 231 b by not less than a coherent length of the lightsource, whereby it is possible to prevent the interference between theelement lenses 231.

FIG. 4B is an embodiment in which λ/4 wavelength plates 233 are providedat an upstream side of the element lenses 231 constituting the lensarray 22. As illustrated, the adjacent λ/4 wavelength plates 233, e.g.,λ/4 wavelength plates 233 a and 233 b are provided so as to havedifferent polarization directions. Moreover, light to be incident on theelement lenses 231 is previously set in a linearly polarized state. Alsowith this configuration, it is possible to prevent the interferencebetween the outgoing lights from the element lenses 231. In thisexample, the outgoing lights from the element lenses 231 arecircularly-polarized lights, which are made different in terms ofpolarized direction (one of the two adjacent element lenses 231 isclockwise, and the other thereof is counter clockwise) to therebyprevent the interference. Alternatively, the light to be incident on theelement lenses 231 is isotopically polarized, and polarization plateshaving different axial directions are provided at the upstream side ofthe element lenses 231. Further alternatively, elements other than theabove that can prevent the polarization states from interfering witheach other may be employed.

The transparent bodies 232 of FIG. 4A and λ/4 wavelength plates 233 ofFIG. 4B may be provided at a downstream side of the element lenses 231,in place of being provided at the upstream side thereof. Also in thiscase, the same effect can be obtained. Moreover, the configuration ofthe embodiment illustrated in FIG. 3 and configuration of the embodimentillustrated in FIG. 4 may be combined.

As the element lenses 231 constituting the lens array 22 used in thepresent embodiment, gradient index lenses may be used. FIG. 5 is a viewillustrating a configuration of the lens array using the gradient indexlenses. The gradient index lens is a lens whose material is madedifferent section by section to change a refractive index. Particularly,in the configuration like the present embodiment, in which the incidentsurface is subjected to scanning, design of the element lenses 231 inaccordance with various conditions of the incident light, such asincident angle can be facilitated. In FIG. 5, a part of the lens array22 constituted by the gradient index type element lenses 231 is showntogether with an optical axis center and an optical path of each elementlens 231.

The optical scanning section 15 constituted by the movable mirror deviceusing the galvano mirror has thus been described with reference toFIG. 1. However, the optical scanning section 15 may be realized using avariable diffraction element or a phase modulation element that does notinclude a movable portion. FIG. 6 is a view illustrating a configurationof the optical scanning section (variable diffraction element) accordingto another embodiment of the present invention, FIG. 7A is a viewillustrating a configuration of the optical scanning section (phasemodulation element) according to another embodiment of the presentinvention, FIG. 7B is a view illustrating a phase change in the opticalscanning section, and FIGS. 8A to 8E are views each illustrating thephase change in the optical scanning section (phase modulation element)according to another embodiment of the present invention.

The optical scanning section 15 of FIG. 6 is an embodiment using thevariable diffraction element. In this embodiment, an amplitudemodulation type liquid crystal element is used as the variablediffraction element. The liquid crystal element constituting the opticalscanning section 15 forms a diffraction grating by liquid crystal 151. Apitch of the diffraction grating formed by the liquid crystal 151 ischanged with time to change a diffraction angle, thereby allowing theemission direction of the coherent light emitted from the light source11 and entering the optical scanning section 15 to be changed with time.In the present embodiment, the coherent light is made to obliquely enteran incident surface of the optical scanning section 15 to allowzero-dimensional light to escape and allow diffracted light to beemitted in a normal direction of the element.

As the variable diffraction element, in addition to the above liquidcrystal element, an optical element, such as an acoustic-opticalelement, that modulates a phase of light passing there through may beused. Alternatively, a micromirror device that modulates a phase oflight to be reflected thereby may be used.

The light scanning section 15 of FIG. 7A is an embodiment using thephase modulation element. In this embodiment, a liquid crystal thatmodulates only a phase is used. As illustrated in FIG. 7A which is aconfiguration view of the light scanning section 15 using the phasemodulation element, the optical scanning section 15 includes a liquidcrystal layer 152 encapsulated between transparent base materials 153and 154. The liquid crystal layer 152 includes pixel electrodes 152 aprovided sectionally and a common electrode 152 b. By sequentiallychanging a refractive index section by section, the phase of transmittedlight can be changed.

FIG. 7B is a view illustrating a basic form of a phase change andrepresenting a phase distribution in correspondence with theconfiguration of FIG. 7A. By changing bias voltage to be applied to thepixel electrode 152 a, a phase distribution as indicated by time t1 andtime t2 can be formed. In such a phase distribution, as illustrated inFIG. 7A, the scanning light La, which is in a state of the scanninglight La (t1) at the time t1, can be deflected into a state of thescanning light La (t2) at time t2. Actually, changing the phase statebetween the time t1 and time t2 in multiple stages or in a continuousmanner allows a direction of the scanning light (La) to be changed inmultiple stages or in a continuous manner.

FIGS. 8A to 8E are views illustrating another embodiment of the phasechange. In this embodiment, the phase distribution is change into aKinoform pattern, that is, a pattern in which the phase is repeatedlychanged between 0π to 2π is changed with time to sequentially change adeflection condition to thereby change a deflection direction as in thecase of FIG. 7B. As is the case with FIG. 7B, FIGS. 8A to 8E eachrepresent a phase distribution in correspondence with the configurationof FIG. 7A. FIG. 8A represents a phase state at the time t1, and FIG. 8Erepresents a phase state at the time t2. By changing with time a phaseshape from FIG. 8A to FIG. 8E and vice versa, the coherent light emittedfrom the light source 11 is deflected. The phase distribution may be setto a Fresnel lens type in which the phase range is a set to a rangeother than from 0π to 2π.

Unlike the above-described variable diffraction element is used for theoptical scanning section 15, zero-order light is not generated when thephase modulation element is used for the optical scanning section 15,light utilization efficiency can be enhanced. Moreover, as illustrated,the coherent light can be made to enter the incident surface of theoptical scanning section 15 at right angles.

According to the present embodiment, there can be provided anillumination device that can make speckle noise less noticeable and aprojection type image display device that can present an image in whichthe speckles noise is less noticeable by illuminating the opticalmodulation element 31 using the illumination device. Particularly, inthe present embodiment, the diverging light diverged by the lens array22 is used to illuminate, through the second optical path conversionsystem 23, the optical modulation element, whereby light utilizationefficiency is enhanced.

The present invention is not limited to the above embodiments, and anembodiment obtained by appropriately combining technical featuresdisclosed in each of the above embodiments is included in the technicalscope of the present invention.

EXPLANATION OF REFERENCE SYMBOLS

-   -   10: Projection type image display device    -   11: Light source    -   15: Optical scanning section    -   151: Liquid crystal    -   152: Liquid crystal layer    -   152 a: Pixel electrode    -   152 b: Common electrode    -   153, 154: Transparent base material    -   21: First optical path conversion system    -   22: Lens array    -   23: Second optical path conversion system    -   231: Element lens    -   232: Optical element (transparent body)    -   233: λ/4 wavelength plate

1-16. (canceled)
 17. A projection type image display device comprising:a light source that emits coherent light; an optical scanning sectionthat scans the coherent light emitted from the light source and changeswith time a direction of the coherent light; a lens array including aplurality of element lenses and configured to diverge the light scannedby the optical scanning section; an optical modulation element having animage formation area in which an image is formed; an optical pathconversion system configured to control a diverging angle of thediverging light to be emitted from respective points of the lens arrayand to allow the diverging light whose diverging angle has beencontrolled to illuminate an area to be illuminated sequentially in anoverlapping manner; and a projection optical system that projects theimage of the optical modulation element on a screen.
 18. The projectiontype image display device according to claim 17, wherein the opticalpath conversion system illuminates the entire area to be illuminatedregardless of a position at which the optical scanning section scans thecoherent light.
 19. The projection type image display device accordingto claim 17, wherein the optical path conversion system includes anoptical element having a light collection function.
 20. The projectiontype image display device according to claim 17, wherein the elementlenses constituting the lens array are each a gradient index lens. 21.The projection type image display device according to claim 17, whereinthe element lenses constituting the lens array are in multiple rows inan optical axis direction thereof.
 22. The projection type image displaydevice according to claim 17, wherein a beam width of the coherent lightthat enters the lens array is smaller than an interval between adjacentelement lenses.
 23. The projection type image display device accordingto claim 17, wherein a polarization control element is provided at anincident side or an emitting side of the lens array so as to preventinterference between beams passing through the adjacent element lenses.24. The projection type image display device according to claim 17,wherein an optical element that provides a difference in optical pathlength so as to prevent interference between beams passing through theadjacent element lenses is provided at the incident side or emittingside of the lens array.
 25. The projection type image display deviceaccording to claim 17, wherein the optical scanning section includes agalvano mirror.
 26. The illumination device according to claim 17,wherein the optical scanning section includes a polygon mirror.
 27. Theprojection type image display device according to claim 17, wherein theoptical scanning section includes a variable diffraction element. 28.The projection type image display device according to claim 17, whereinthe optical scanning section includes a phase modulation element. 29.The projection type image display device according to claim 17, whereina beam forming means is disposed between the light source and opticalscanning section.
 30. The projection type image display device accordingto claim 17, wherein focal planes of the element lenses of the lensarray and a pupil surface of the projection optical system are kept insubstantially a conjugate relationship.